fix(graph_trace_helper): no self-loop for a one-hop neighbor sharing our prefix; survive bad distances

Codex re-review follow-up. The one-hop shortcut wrote dd->dd both ways when the neighbor shares the bot's prefix; it now skips the update, as the multi-hop path does. A distance error (a stored infinite latitude) no longer drops the trace's edges; the edge is recorded without a distance, as before the rewrite.

modules/graph_trace_helper.py

@@ -100,6 +100,10 @@ def update_mesh_graph_from_trace_data(
 
     if is_immediate_neighbor:
         neighbor_prefix = path_hashes[0].lower()
+        if neighbor_prefix == bot_prefix:
+            # The graph, keyed by prefix, can't tell this neighbor from the bot
+            bot.logger.debug(f"Mesh graph: Neighbor {neighbor_prefix} shares the bot's prefix, skipping trace update")
+            return
         neighbor_key = None
         try:
             count_query = f"""
@@ -208,9 +212,12 @@ def update_mesh_graph_from_trace_data(
         geographic_distance = None
         from_location, to_location = locations[i], locations[i + 1]
         if from_location and to_location:
-            geographic_distance = calculate_distance(
-                from_location[0], from_location[1], to_location[0], to_location[1],
-            )
+            try:
+                geographic_distance = calculate_distance(
+                    from_location[0], from_location[1], to_location[0], to_location[1],
+                )
+            except Exception as e:
+                bot.logger.debug(f"Could not calculate distance for trace edge {from_node}->{to_node}: {e}")
         mesh_graph.add_edge(
             from_prefix=from_node,
             to_prefix=to_node,

tests/test_graph_trace_helper.py

@@ -377,3 +377,19 @@ class TestOwnTraceChain:
         assert [(c["from_prefix"], c["to_prefix"]) for c in calls] == [("dd", "aa"), ("aa", "dd")]
         assert calls[0]["from_public_key"] == "dd" * 32
         assert calls[1]["to_public_key"] is None  # the hop "dd", not the bot
+
+
+    def test_a_neighbor_sharing_the_bots_prefix_adds_no_self_loop(self):
+        bot = _make_bot(bot_prefix="dd")
+        update_mesh_graph_from_trace_data(bot, ["dd"], {}, is_our_trace=True)
+        bot.mesh_graph.add_edge.assert_not_called()
+
+    def test_a_bad_stored_location_still_records_the_edges(self, monkeypatch):
+        import modules.utils as utils
+
+        bot = _make_bot(bot_prefix="dd")
+        monkeypatch.setattr(utils, "_get_node_location_from_db", lambda *a, **k: ((float("inf"), 0.0), None))
+        monkeypatch.setattr(utils, "calculate_distance", Mock(side_effect=ValueError("math domain error")))
+        update_mesh_graph_from_trace_data(bot, ["aa", "bb"], {})
+        assert bot.mesh_graph.add_edge.call_count == 2
+        assert all(c.kwargs["geographic_distance"] is None for c in bot.mesh_graph.add_edge.call_args_list)